Induction furnace



P. H. BRACE INDUCTION FURNACE April 28, 1931.

Filed NOV. 1, 1929 ATTORNEY mr m wH l r. m m P Fig.4. Fig.5

Patented Apr. 28, 1931 UNITED- STATES PATENT OFFICE PORTER H. BRACE, OF FOREST HILIiS BOROUGH, PENNSYLVANIA, ASSIGNOR T0 WEST-- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA IN DUGTION FURNACE Application filed November 1, 1929. Serial No. 404,013.

My invention relates to electric furnaces and, more particularly, to electric furnaces of the induction type.

An object of my invention is to provide a highly efficient induction-furnace equipment particularly adapted to relatively large furnaces and also adapted to be operated at relatively low frequencies.

Another object of my invention is to provide an induction-furnace structure having a surrounding laminated structure and means closely associated with the laminated structure for supporting the roof of the crucible.

Another object of my invention is to provide an induction-furnace structure having a laminated magnetic member that is artificially fluid cooled.

Another object of my invention is to provide an induction-furnace structure having a substantially closed crucible or lining for material tobe melted and having also a pouring spout located intermediate the ends of the crucible, together with energizing coils shaped to conform to the pouring-spout location.

In practicing my invention, I provide a crucible or lining for a bath that shall be relatively shallow in axial depth and that shall be partially or entirely surrounded by a laminated structure extending axially and radially around the crucible. Relatively heavy metal plates, of substantially the same contour as the laminations, are provided with means interfitting with the refractory roof members of the crucible to support the same. A plurality of relatively thin sheetmetal plates of relatively high heat conductivity are fluid cooled and interfit with the laminations at one edge thereof; A plurality of energizing coils are located in axially superposed position and are also fluid cooled.

In the single sheet of drawings,

Figure 1 is a view, in vertical section through a furnace embodying my invention, taken on the line II of Fig. 2;

Fig. 2 is a top plan View of the furnace, a portion of the'top being broken away to show details of construction;

Fig. 3 is a fragmentary sectional View, taken on the line IIIIII of Fig. 1;

Fig. 4 is a view, in lateral section, of one form of electric conductor, and

Fig. 5 is a View, in lateral section, of a modi- '55 fied form of electric-current conductor.

A furnace structure, designated generally by the numeral 11, comprises an outer metal casing consisting of two portions 12 and 13, shown more particularly in plan view in Fig. 2 of the drawings.

A laminated structure includes a plurality of laminations 14 which may be either of substantially rectangular shape or may be built up of two portions each of substantially C shape. I have indicated two portions, each of C shape, in Fig. 1 of the drawings but it is to be understood that the laminated structure may be composed of a plurality of individual sections or segments of laminated sheet steel, in accordance with the size of the furnace and the maximum size of steel sheets available for such purposes. The

. shape of the intermediate portion of the upper set of laminations is made substantially as shown in Fig. 1 of the drawings so that they may be relatively close to the material to be heated, as well as for another purpose to be hereinafter set forth.

A plurality of relatively thick and heavy sheet-metal plates 16, 17 and 18 are provided, which may or may not be of substantially the same contour as the laminations 14. The relatively heavy metal sheets may extend downwardly at the top portion thereof, as is shown in Fig. 1 of the drawings, for a purpose to be hereinafter set forth. I prefer to make the metal plates 16, 17 and 18 of nonmagnetic material in order to reduce the eddy-current losses therein to as great an extent as possible.

A refractory crucible 19 is provided, the bottom portion of which is supported by the laminations 14 and the relatively heavy metal plates 16, 17 and 18. The crucible may either be made in one piece or it may be composed of a-plurality of suitably shaped bricks or blocks, the latter construction being shown in the drawings.

I prefer to provide a roof 21 composed of ings.

suitable refractory bricks or blocks shaped to so cooperate with the peripheral wall structure of the crucible as to substantially cover the bath of molten material. The metal plates 16, 17 and 18 and the roof 21 are provided with interfitting portions, shown as cooperating dovetails in Fig. 1 of the drawings, in order that the roof may be supported by the plates 16, 17 and18.

A pouring spoutis provided to surround an opening 22 which is located intermediate the ends of the core 14.

An energizing coil, designated generally by the numeral 23-, surrounds the crucible and may be located in, and surrounded by, suitable granular electric-insulating and heat-insulating material 24 located between the outer surface of the annular portion of the crucible and the casing portions 12 and 13 or the inside of the laminated structure 14. I preferably employ a relatively thin copper conductor of relatively great width, as is shown in Fig. 4 of the drawings and designated by numeral 26, a tube 27 being closely associated with one edge of the conductor 26, the tube 27 being utilized to conduct a cooling fluid to suitably cool the current-traversed coil 23.

It may be desirable to subdivide the conductor, the greatest dimension of which extends axially of the crucible, and such a structure is shown in Fig. 5 of the drawings. conductor 28 is therein shown as embodying two portions, each being similar to the conductor 26 of Fig. 4, except that the width of each of the portions 29 and 31 is not as great as that of conductor 26. A tube 32 is located between the conductor portions 29 and 31 and all three members closely associated in order that a cooling fluid traversing the tube 32 shall cool both conductor portions 29 and 31. I provide also means for artificially cooling the laminations, more particularly at the bot tom portion thereof, and reference may be had to Fig. 3 of the drawings which shows, on an enlarged scale, the bottoms of the laminations 14. I prefer to'make the alternate laminations of different widths in order thata plurality of sheets 33 of copper may interfit therewith. The relatively narrow sheets of copper 33 are perforated near the outer edges thereof to receive tubes 34, as shown in Fig. 1 of the drawings, the individual tubes being connected by conduits not shown in the drawings, in order that a cooling fluid may traverse them to cool both the copper sheets 33 and the laminations 14. r

In order that relatively little, if any, of the flux enerated by current traversin the coil 23 s all return through either 0% the casing portions 12 and 13, I prefer to employ radially-extending relatively narrow sheetsteel laminations 36, as shown in the upper right-hand portion of Fig. 2 of the draw- While I have not shown such laminations as extending between other portions of the casing 12 and the coil or between the casing portion 13 and the coil, it is to be understood that such is actually the case.

While I have shown no means for clamping together the casing portions 12 and 13, the laminations 14 and the plates 16, 17 and 18 at diametrically opposed places, it is to be understood that any suitable or desired clampthe crucible such that the deptho the metal in the crucible or hearth is less than one and one-half times the maximum diameter of the hearth, that is, the depth of metal is relatively shallow, as compared with its diametral extent.

I prefer also to make the axial length of the energizing coil relatively large, as compared with the maximum depth of the metal within the crucible and to employ a plurality of fiat spiral coils which are axially superposed one above another. I have found that, in a construction of this kind, in which the coils are partially enveloped by a laminated A magnetic structure, it is possible to provide a relatively large radial space between the coil and the molten metal without serious loss in efiiciency. This, of course, means that the radial thickness of the wall of the crucible or lining may be relatively large and that the insulation between adjacent turns of the energizing coil may also be relatively large and still obtain relatively high power factor and efficiency in actual operation of large furnaces.

It may be noted that certain of the energizing coils and, more particularly, certain portions of the upper coils are bent upwardly in order to be located above the pouring spout, and that other coils have portions bent downwardly to be located below the pourin spout. This assists in maintaining the cruci le substantially closed without any great inconvenience in introducing the raw material to be melted or in removing the molten material from the crucible, this structure, at the same time molten material, thereby increasing the efficiency of operation of the furnace.

The depressed central portion of the upper laminations is located below the raised ortion of the upper coils, and the location 0 the at the bottom of the furnace, although this is assisting in retaining the heat in the more difiicult of construction than when used gizing coil surrounding the crucible, said coil at the top, as shown. aving one portion bowed upwardly to be 10- The device embodying my invention procated in substantially the same plane as the vides also an artificially cooled magnetic depressed portion of the laminations. structure which has associated therewith a In testimony whereof,Ihave hereunto subplurality of metal plates for directly supportscribed my name this 28th day of October, ing the roof and aiding also in preventing 1929. harmful vibrations of the furnace structure. PORTER H. BRACE.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed bythe prior art or are set forth in the appended claims.

I claim as my invention:

1. In an induction-furnace structure hav, ing a crucible of the pot type, a laminated magnetic structure extendin around the crucible, metal plates at the si es of the laminated structure, a refractory roof for the crucible, and means integral with the roof and the metal plates for supporting the roof from the plates.

2. In an induction-furnace structure having a crucible ofthe pot type, a laminated magnetic structure extending around the crucible, metal plates at the sides of the laminated structure, a refractory roof for the crucible, and interlocking means on said plates and said roof for supporting the roof from the plates.

3. In an induction-furnace structure having a crucible of the pot type and a radiallyextending covered pouring spout located intermediate the ends of the crucible, and a plurality of sets of energizing coils surrounding the crucible, portions of certain of the uppermost coils extending above the spout.

4. In an induction-furnace structure have I ing a crucible of the pot type, a laminated magnetic structure extending around the crucible, an energizing coil surrounding the crucible and within the laminated magnetic structure, and fluid-traversed cooling means interleaved with the magnetic structure.

5. In an induction-furnace structure having a crucible of the pot type, a laminated magnetic structure extending around the crucible, an energizing coil surrounding the crucible and within the laminated magnetic structure, and fluid-traversed cooling means interleaved with the magnetic structure at the bottom edge only.

6. In an induction-furnace structure having a crucible of the pot type, a laminated magnetic structure extending around the crucible and having a. top portion extending into the crucible, and an energizing coil surrounding the crucible.

7. In an induction-furnace structure having a crucible of the pot type, a laminated magnetic structure extending around the crucible and having a portion extending into the crucible at the top thereof, and an ener- 

